1. Field of the Invention
The invention relates to reinforced polymeric laminates. More particularly, the present invention is related to corrosion resistant reinforced thermosetting plastic laminates, and a surfacing veil for incorporation in the laminates.
2. Description of the Related Art
The use of surfacing veil as the primary corrosion barrier in thermoset resin fiber reinforced laminates is well known in the glass fiber reinforced plastic industry.
In the American Society for Testing and Materials (hereinafter ASTM) C 582-87 entitled Standard Specification for Contact-Molded Reinforced Thermosetting Plastic (RTP) Laminates for Corrosion Resistant Equipment, which is incorporated by reference, contact molding is defined in section 3.4 as ". . . a method of fabrication wherein the glass-fiber reinforcement is applied to the mold, in the form of chopped-strand mat or woven roving, by hand or from a reel, or in the form of chopped strands of continuous-filament glass from a chopper-spray gun. The resin matrix is applied by various methods, including brush, roller, or spray gun. Consolidation of the composite laminate is by rolling."
A surfacing veil or mat is defined in ASTM C 582-87, ASTM D 4097-88, and ASTM D 3299-88. A surfacing veil or mat is defined in ASTM C 582-87, section 5.2.1 of ASTM C 582-87 as "a thin mat of fine fibers used primarily to produce a smooth surface on a reinforced plastic." 5.2.1.2 of ASTM C 582-87 states that the requirements of acceptable surface veils are:
"(a) Resin compatibility. PA1 (b) Uniform fiber distribution. PA1 (c) Single filaments (not bunched) PA1 (d) The veil layer(s) shall be a minimum of 10 mils in dry thickness producing a 10 to 15 mil resin saturated veil layer per 10 mils of dry veil, and PA1 (e) Minimum fiber length shall be 0.5 in. Note 9--The chemical resistance of the RTP laminate is provided by the resin. In combination with the cured resin, the surfacing veil helps determine the thickness of the resin-rich layer, reduces microcracking, and provides a nonwicking chemically resistant layer. PA1 (a) Drapability (surfacing veil should conform to mold shape). PA1 (b) Dry and wet tensile strength. PA1 (c) Binder solubility (if used) PA1 (d) Uniform wetting. PA1 (e) Surfacing veil shall wet-out completely without trapping air during laminating, and PA1 (f) Surfacing veil should not inhibit resin cure."
Additional desirable considerations in choosing a veil for a specific application include:
The surfacing veil is a reinforcement material that when saturated with resin (sometimes referred to as "wet out") retains a high resin to reinforcement ratio. Thermoset resin is very chemically resistant and the surfacing veils of the prior art are in many cases susceptible to attack by the chemical being contained. If the surfacing veils of the prior art are exposed to the chemical contained due to a breach in the resin, attack of the reinforcement material may start, leading to a shortened service life and equipment failure.
Surfacing veils of the prior art are commonly made from monofilament glass or polyester fibers. The most commonly used monofilament glass fibers are known in the art as "C" glass. The most commonly used polyester fibers used for surfacing veil are sold by E. I. Dupont de Nemours & Co. under the trademark Dacron.
Exemplary of the related art are the following U.S. Patents:
U.S. Pat. No. 5,077,115 discloses thermoplastic composite material including a thermoplastic matrix which is highly filled with a coated ceramic filler. In an important feature of the present invention, the ceramic filler has been coated with a rubbery polymer that bonds to the filler. In a preferred embodiment, the thermoplastic matrix comprises a fluoropolymer, preferably a chlorofluoropolymer and the ceramic filler is a fused amorphous silica coated with a rubbery polymeric material. The thermoplastic composite material of this invention exhibits numerous advantages which makes it well suited for use as a bonding film, particularly a bonding film for producing multilayer printed wiring bonds.
U.S. Pat. No. 4,943,473 discloses flexible laminated fluoropolymer-containing composites including fire and chemical resistant, flexible composites made from flexible woven, non-woven and knitted substrates and fluoropolymer containing films. Adhesives, such as melt adhesives, may be used in making the composites. The composites are suitable for use in protective garments, and in other articles where flexible chemically resistant materials are needed. A seaming technique for use in protective articles is disclosed.
U.S. Pat. No. 4,886,699 discloses a glass fiber reinforced fluoropolymeric circuit laminate including one or more layers of fluoropolymer impregnated woven glass cloth sandwiched between one or more layers of "random" microfiberglass reinforced fluoropolymer. This composite of fluoropolymer, woven glass fabric and random glass microfibers may be clad on one or both outer surfaces with a suitable conductive martial such as copper or certain known resistive foils. The fluoropolymer impregnated woven glass layer or layers will be nested between microfiberglass reinforced fluoropolymer layers to provide the outer surfaces of the circuit with smooth surfaces for fine line circuitry. The circuit laminate of the invention exhibits good dimensional stability, smooth surfaces for fine line circuitry, good electrical properties, and strong foil and interlaminar adhesion properties.
U.S. Pat. No. 4,886,689 discloses a matrix-matrix polyblend adhesives and method of bonding incompatible polymers useful in an adhesive tie layer to bond incompatible polymer layers. The adhesives are a blend of the components making up the incompatible polymer layers themselves, or polymers substantially similar to these, and are melt processed to produce a matrix-matrix morphology with mechanical interlocking of the polymer components that is maintained upon cooling. Additives may be provided in one or both adhesive components to improve the cohesive strength of the adhesive formed by the mechanical interlocking.
U.S. Pat. No. 4,777,351 discloses devices including conductive polymer compositions. A number of improvements to electrical devices, particularly sheet heaters, including conductive polymer compositions, are provided the preferred heater has the following features (a) it includes a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it includes a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it includes a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it includes a dielectric layer intimately bonded to the resistive element and to the electrodes.
The invention also provides an electrical device including first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.
U.S. Pat. No. 4,770,927 discloses a reinforced fluoropolymer composite which includes a substrate having a coating matrix including an initial layer of a perfluoropolymer and an overcoat including a fluoroelastomer, a fluoroplastic, a fluoroelastomer/fluoroplastic blend, or a combination thereof. The perfluoropolymer in the initial layer may be a perfluoroplastic, a perfluoroelastomer, or blends thereof. In a separate embodiment, the novel composite includes a substrate coated solely with one or more layers of perfluoroelastomer alone or as a blend with a perfluoroplastic. Where the substrate is not susceptible to hydrogen fluoride corrosion, the composite may include solely one or more layers of a blend of a fluoroelastomer and a hydrogen-containing perfluoroplastic. Cross-linking accelerators may be used to cross-link one or more of the resins contained in the coating layers. Each composite may be top-coated with a layer or layers of a fluoroplastic, fluoroelastomer, and/or a blend thereof. The composite is flexible, exhibits good matrix cohesion and possesses substantial adhesion to the material acting as the reinforcement or substrate. A method for making such a composite includes the unique deployment of a perfluoropolymer directly onto the substrate in a relatively small amount sufficient to protect the substrate from chemical corrosion without impairing flexibility, followed by the application of the overcoat layer.
U.S. Pat. No. 4,677,017 discloses coextrusion of thermoplastic fluoropolymers with thermoplastic polymers. The coextruded film includes at least one thermoplastic fluoropolymer layer and at least one thermoplastic polymeric layer adjacent to the to the thermoplastic fluoropolymer layer. There is preferably a coextruded adhesive layer between each thermoplastic fluoropolymer layer and each thermoplastic polymeric layer. The coextruded film can be oriented in at least one direction and/or embossed without delamination, fibrillating, or splitting.
U.S. Pat. No. 4,539,113 discloses a fluororesin filter made entirely of fluororesin having both a high corrosion and high heat resistance. A plurality of tubular filtering elements are arranged in a fluororesin container. Each tubular filtering element has a polytetraethylene tubular filtering film closed at one end and arranged over or inserted into a fluororesin tubular support. The tubular filtering elements are connected to a cover structure, on the inner surface of which is formed a groove for communicating the tubular filtering elements to one of the liquid inlet and liquid outlet provided in the cover structure.
U.S. Pat. No. 4,505,971 discloses a fluoroplastic and metal laminate having rubber compound bonded layers, and a process and composition for adhering a rubber compound to a fluoroplastic and/or to metal. The invention contemplates the use of separate sequentially applied adhesive layers to the fluoroplastic or metal substrate. The last applied layer, a rubber cement, allows the metal or fluoroplastic to be adhered to the uncured rubber compound which is subsequently vulcanized. The invention finds particular utility in securing a fluoroplastic and a rubber lining to steel or other metallic surfaces. A typical use is the lining of the interior of a railroad tank car, providing protection from corrosive or hostile environments experienced when the tank car is transporting acids or other caustic materials. Other uses include the lining of chemical process vessels and piping.
U.S. Pat. No. 4,163,505 discloses foldable liners for fluids holding storage tanks which are polyhedrical shaped liners, mounted vertically inside a cylindrical storage tank, and fixed to the inner top of the tank.
The lower portion of the liner is fitted to a rigid frame which is free to displace in the vertical direction.
Devices located on equidistant horizontal narrow strips of the liner, restrain the strips from displacing radially inward but allow them to move in the vertical direction.
Devices that apply forces directed vertically upwards over the rigid frame and of sufficient magnitude to produce critical compressive stresses in the liner are provided.
These critical compressive stresses induce buckling of the portions of the liner between successive narrow strips, and folding of the liner-in-situ is achieved.
U.S. Pat. No. 3,833,453 discloses a nonflammable, fiber-filled, cold-formable thermoplastic sheets which are glass fiber-reinforced ethylene chlorotrifluoroethylene composite sheets formable into shaped objects in a mold at ambient temperatures solely by moderate preheating of the sheet outside of the mold. This polymer including a high molecular weight, tough copolymer of ethylene and chlorotrifluoroethylene in an approximate 1:1 mol ratio is inherently non-flammable in air. A glass fiber of controlled length increases the mechanical properties of the composite structure and allows fabrication into suitable shapes without detracting from the nonflammable properties of the polymeric composite.